title: Monolithic bifocal zone-plate lenses for confocal collimation of laser diodes.
abstract: An elliptical monolithic bifocal zone plate as a collimating lens, whose two focal lengths in the orthogonal directions match the different beam waist positions of the fast and slow axes' light from edge-emitting laser diodes, is proposed and experimentally demonstrated by employing femtosecond laser direct writing technology. The high-quality eight-level zone plate exhibits a diffraction efficiency of 92.9%, which is much higher than those ever reported. Shaped by the elliptical lens, the laser diodes' divergence angles are simultaneously reduced from 65° (1134 mrad, fast axis) and 24° (418 mrad, slow axis) to 7.7 and 136.5 mrad, respectively.
authors.forename: Tong
authors.initials: T
authors.lastname: Jiang
authors.forename: Qi-Dai
authors.initials: QD
authors.lastname: Chen
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
authors.forename: Zhen-Nan
authors.initials: ZN
authors.lastname: Tian
authors.forename: Li-Gang
authors.initials: LG
authors.lastname: Niu
authors.forename: Qi-Song
authors.initials: QS
authors.lastname: Li
authors.forename: Hai-Yu
authors.initials: HY
authors.lastname: Wang
authors.forename: Li
authors.initials: L
authors.lastname: Qin
authors.forename: Hong-Bo
authors.initials: HB
authors.lastname: Sun